In the pursuit of higher motor engine performance, automobile engineers have for the last few years introduced engines with multiple valves per cylinder (usually four), which in a four-cylinder car add up to a 16-valve engine, or 32 in a V-8. There are two sets of valves in an engine: intake valves that open to let the fuel-air mixture into the cylinder, and exhaust valves that open to expel the combustion fumes. The use of multiple valves increases the efficiency of the exchange of gases. That allows an engine to breathe maximum output at high revolutions per minute (rpm). Their intake and exhaust valves open for longer (valve timing) and further (valve lift) than the engines in ordinary car; on the other hand, engines in ordinary cars obtain maximum performance at lower rpm. The lobes on the revolving camshafts of an engine push down the rocker arms to open the valves in the necessary sequence and at the proper time.
The engine valves each defines a valve head plate carried by an elongated stem substantially orthogonal to the plane thereof. Usually, the valve head--and therefore the valve port opening in the engine cylinder head--is of circular shape in plan view, whereby the valve stem is not for that reason precluded from rotating within the valve stem channel in the cylinder head, since, in the valve port closing position thereof, the circular (disc-shape) head sits onto an annular cavity of the valve port (inwardly of the combustion chamber).
However, in a recent breakthrough, non circular valve heads for internal combustion engines, together with correspondingly shaped valve head seats about the valve port openings thereof, have been developed. More specifically, U.S. Pat. No. 4,790,272 issued in December 1988 to Woolenweber, discloses and claims poppet valves for internal combustion engines, having various shapes, including semi-circular, quadri-circular, oval and elliptical shapes. Woolenweber claims that such valves increase the flow-through area across the engine intake and exhaust valves, increase the air quantity available in the cylinder assembly for combustion, reduces the throttling loss experienced by the cylinder assembly, increases the extent of combustion of the air-fuel mixture introduced into the cylinder assembly, reduces engine pumping losses, increases the power output of the engine, reduces the amount of residual hydrocarbons and carbon monoxide present in the exhaust gases, and provide overall a more efficient internal combustion engine, notably if it is turbocharged. Needless to say, such a valve cannot and should not rotate about the axis of its single stem, within the cylinder head stem guide channel. Indeed, if Woolenweber's valve was allowed to rotate even for a small angular value, the combustion chamber of the cylinder would not be sealed, and thus the gas compression in the combustion chamber would be very much compromised while the valve itself would rapidly become destroyed. Also this valve requires a single or two coaxial large diameter springs which take more room widthwise in the cylinder head.